The real question is whether it's a good thing to stop "mind wandering" when it hasn't reached the level of disorder. From the perspective of evolution, it almost certainly has a purpose. Paul Graham pointed out that its probably useful for problem solving:
I wonder if it would be good to have the ability to better focus one's self when one's mind is wandering into unproductive subjects (e.g. agonizing over an ex) without necessarily getting to the point where your default mode has been changed so much as to prevent insights in the shower (and instead being deeply aware of the hot water).
http://www.paulgraham.com/top.html
I wonder if it would be good to have the ability to better focus one's self when one's mind is wandering into unproductive subjects (e.g. agonizing over an ex) without necessarily getting to the point where your default mode has been changed so much as to prevent insights in the shower (and instead being deeply aware of the hot water).